Excepting Judas Iscariot (who hung himself after betraying Jesus), one of the most powerful witnesses to the Resurrection of Jesus has to do with how it powerfully, and instantly, changed his disciples.
Immediately after His Crucifixion, they were all hiding out behind locked doors like trembling bunnies, terrified that the Romans and religious leaders were scouring the countryside, seeking to find, arrest and crucify them as well. But then, the most amazing transformation happened to them all - which only seeing and talking to the risen Lord Jesus can explain. Because AFTER His Resurrection back to life, after his brutal death, and they had seen, talked to, and broken bread with Him, these trembling men were all instantly turned into bold, courageous testifiers to their risen Savior and began to spread the Gospel message. As they well knew doing so might well bring them a horrific death as well - as it later did, for most of them.
And in a powerful testimony to what they unquestionably knew about Jesus' rising from the dead, ( SEE THIS VIDEO ) to learn what happened to the disciples the Church recorded the deaths of.
As for competing historical narratives denying the martyrdom of the disciples we know about - SEE THIS ANALYSIS from nationally renowned, cold-case homicide detective J. Warner Wallace, who is today a professor of Christian apologetics at Biola University and Southern Evangelical Seminary, who became a Christian at age 35 after using his detective skills to investigate the claims about Jesus found in the Gospels!